In recent times, electronic components to be mounted to devices, for instance, cellular phones and the like have also been made compact in accordance with considerable downsizing of the devices. There is a bump forming apparatus which forms bumps to electrode parts of circuit formation parts provided on a semiconductor wafer without cutting each of the individual circuit formation parts from the semiconductor wafer. The bump forming apparatus of this type includes a carry-in device for taking out a semiconductor wafer before having bumps formed from a first storage container in which the semiconductor wafers before having bumps formed are stored, a second storage container for storing wafers after having bumps formed, a bonding stage on which the wafer before having bumps formed is placed to heat the wafer normally to approximately 150° C. so as to bond the electrode parts and the bumps, a carry-out device for storing the wafer after having bumps formed into the second storage container, and a shift device for moving the wafer from the carry-in device to the bonding stage and from the bonding stage to the carry-out device.
Meanwhile, bonding between each electrode part and the bump becomes incomplete in some cases, e.g., in piezoelectric substrates to which SAW (Surface Acoustic Wave) filters to be used in the aforementioned cellular phones or the like are formed, or in semiconductor substrates having micro bumps formed. Namely, as shown in FIG. 45, the SAW filter 10 has pairing input side circuit 12 and output side circuit 13 each formed in the shape of comb teeth on a piezoelectric substrate 11, and a function in which a vibration generated at the input side circuit 12 propagates to the output side circuit 13 which in turn outputs an output based on the propagated vibration. On this basis, the SAW filter passes only signals of a specific frequency. Due to the structure and the function of the SAW filter 10, film thicknesses at circuit formation parts of the input side circuit 12 and the output side circuit 13 shaped like comb teeth and at electrode parts of these circuits 12 and 13 are defined to be approximately 2000 Å, which is thinner than a film thickness of electrode parts formed on a normal semiconductor substrate of, e.g., Si of approximately 5000-7000 Å. Since a layer of metal material particles forming the electrode parts, for example, of aluminum particles is thin, the bonding between the bumps and the electrode parts is consequently considered to be incomplete in some cases.
In FIG. 46, a diameter 16b of a base part 16a of the bump 16 formed on the electrode part 15 of the micro bump form semiconductor substrate 14 referred to above is approximately 40-48 μm. The bump 16 itself is thus smaller than a bump of the normal semiconductor substrate in which the base diameter is approximately 80 μm. Therefore, a bonding area between the bump 16 and the electrode part 15 is small, so that there are many cases of incomplete bonding.
As one way for supporting the recent miniaturization in electronic devices, there is, for instance, a method whereby electrodes of a semiconductor chip cut from the semiconductor wafer are arranged opposite and connected to electrode parts on a circuit board without using wires. For adopting this method, bumps 52 of gold or the like are formed on electrodes 51 of the semiconductor wafer or the semiconductor chip while the semiconductor wafer and the semiconductor chip are heated, as shown in FIG. 63.
Moreover, the semiconductor chip itself has been made very small to meet the above miniaturization, whereby a heat resisting temperature of the semiconductor chip tends to decrease. A heating temperature at the bump formation is required to be lowered accordingly.
The present invention is devised to solve the above-described problems, and has for its object to provide a bump forming apparatus and a bump formation method in which a bonding strength between bumps formed to electrode parts and electrodes can be improved as compared with the conventional art. More specifically, the present invention has the following objects.
A first object of the present invention is to provide a bump forming apparatus, a bump formation method executed by the bump forming apparatus, a computer readable recording medium having a program recorded therein whereby the bump formation method can be executed, and a bump-formed semiconductor substrate with bumps formed. A bonding state between electrode parts and bumps can be stabilized and a bonding strength can be improved in comparison with the conventional art.
A second object of the present invention is to provide a device and a method for improving a bump strength, and a bump forming apparatus, whereby a quality of semiconductor components can be improved as compared with the conventional art without decreasing a bonding strength between bumps formed on electrodes of the semiconductor components and the electrodes even when the heating temperature at a bump formation is lowered.